The present invention relates to an apparatus for examining a certain abnormality in an object to be measured, such as a disease in the brain, by making use of light.
Apparatus are known that examine diseases in various body organs such as the brain by making use of light. FIG. 5 illustrates an application of the examination apparatus disclosed in U.S. Pat. No. 4,281,645. As shown, a plurality of light launching fibers L.sub.1 -L.sub.6 for guiding light beams emitted from the corresponding number of light sources and a plurality of light pickup fibers S.sub.1 -S.sub.6 that are associated with the fibers L.sub.1 -L.sub.6 are attached to the head. The pickup fibers S.sub.1 -S.sub.6 are located on positions that are opposite to those of the associated launching fibers L.sub.1 -L.sub.6 in such a way that near infrared light beams launched into the head through fibers L.sub.1 -L.sub.6 will be guided to a photodetector for detecting the quantity of light that has been transmitted through the head.
In the apparatus shown in FIG. 5, near infrared light beams are sequentially launched from fibers L.sub.1 -L.sub.6, and the quantities of light that are transmitted through the head and emerge from the pickup fibers S.sub.1 -S.sub.6 that are associated with the fibers L.sub.1 -L.sub.6 are sequentially detected with the photodetector. On the basis of the quantities of transmission light that have been guided by the pickup fibers S.sub.1 -S.sub.6 and detected by the photodetector, the absorption of near infrared light by hemoglobin in the brain is calculated to determine the temporal or time-dependent change in cerebral blood flow and the oxygen saturation in blood. This enables the measurement of light absorption at various sites in the brain on the straight lines that connect the launching fibers L.sub.1 -L.sub.6 and the pickup fibers S.sub.1 -S.sub.6.
As described above, the light launching fibers L.sub.1 -L.sub.6 in the prior art examination apparatus correspond in a one-to-one relationship to the light pickup fibers S.sub.1 -S.sub.6. Therefore, in order to achieve high-sensitivity detection of the light absorbance at sites in the brain on the straight line that connects a certain launching fiber, Say, L.sub.1 and the corresponding pickup fiber, say, S.sub.1, the amount of light emitted from the light source connected to the launching fiber L.sub.1 has to be increased. As a further problem, the prior art apparatus is not suitable for precise detection because the slight shift in the directions or positions of the fibers L.sub.1 and S.sub.1 will cause a great variation in the result of detection. There is also a problem that in the brain the direction of light travel is considerably disturbed by scattering.